Photographic shutter with reciprocating shutter blade driving member and electronic timing device

ABSTRACT

A photographic shutter having a driving member which when moved from a normal position opens and then closes the shutter by means of a reciprocating actuating member, an electronic timing device controls an armature lever biased by a return spring with the aid of a photoelectric resistor in dependence upon the ambient light. The armature lever cooperates with a pawl blocking the actuating member in the open position of the blades for the duration of the timing. A switch is connected in the circuit of the electronic timing device and closes a contact when the cocking mechanism of the camera is actuated, the contact short circuiting the photoelectric resistor.

United States Patent 72] Inventor Waldemar T. Rentschler Calmbach,Germany [2]] Appl. No. 772,571

[22] Filed Nov. 1, 1968 [45] Patented Feb. 2,1971

[73] Assignee Prontor-Werk G.m.b.H.

Calmbach, Germany [54] PHOTOGRAPHIC SHUTTER WITH RECIPROCATING SHUTTERBLADE DRIVING MEMBER AND ELECTRONIC TIMING DEVICE 3 Claims, 4 DrawingFigs.

[52] U.S.Cl 95/10 [51] G03b 7/08 [50] Field ofSearch ..95/1OC, 31, 53

[56] References Cited UNITED STATES PATENTS 3,326,103 6/1970 Topaz95/10(C) 3,367,251 2/1968 Furuta 3,422,738 1/1969 Morietal.

95/C1X 95/10(C) ABSTRACT: A photographic shutter having a driving memberwhich when moved from a normal position opens and then closes theshutter by means of a reciprocating actuating member, an electronictiming device controls an armature lever biased by a return spring withthe aid of a photoelectric resistor in dependence upon the ambientlight. The armature lever cooperates with a pawl blocking the actuatingmember in the open position of the blades for the duration of thetiming. A switch is connected in the circuit of the electronic timingdevice and closes a contact when the cocking mechanism of the camera isactuated, the contact short circuiting the photoelectric resistor.

PATENTEU F512 1971' SHEET 2 OF 2 IN VE N TOR Waldemar 7. RenIsch/er BYMarch Gillelie8 WyaH A TTOR NE Y5 PHOTOGRAPHIC SHUTTER WITHRECIPROCATING SHU'I'I'ER BLADE DRIVING MEMBER AND ELECTRONIC TIMINGDEVICE The invention concerns a photographic shutter the driving memberof which in moving from a normal position, moves the blades first intoan open and then into a closed position by means of a reciprocatingactuating part, an electronic timing device being provided whichincludes a photoelectric resistor and controls an armature lever biasedby the action of a return spring in dependence upon ambient lightconditions. The driving member cooperates with a stop lever locking theactuating part of the blades for the duration of the timing operation.

When taking photographs with electronic timing depending on ambientlight, very long exposure times may .result with poor light, so that thephotographer, concluding that exposure has terminated, may attempt torecock the shutter. Since the blade ring is locked in the open positionof the blades for the duration of timing, the return of the drivingmechanism to the cocked position is not possible because of theengagement of the blade ring and the member driving it, until the ringreturns to normal at the end of the exposure. If the photographer isignorant of the lockup mentioned above and exerts force, then parts ofthe blocking gear train may be damaged or broken.

In order to break in to the automatic exposure action already begun,i.e. to terminate the timing procedure indepen dently of the switchingdevice, a switch connected parallel to the photoelectric resistor andactuated by means of a manually actuated button has already beenproposed. This switch is suitable for terminating the timing procedurebut does not prevent damage to the gear train of the said cockingmechanism if the photographer ignores the switching state of theelectronic timing device and tries to cock the shutter.

It is an object of the present invention to actuate the switchterminating the timing of an electronic shutter in dependence uponcertain constantly repeated operational manipulations. For this purposethe invention provides a switch in the circuit of the electronic timingdevice, actuated independently of the cocking mechanism of the camera,which closes a short circuit across the photoelectric resistor. In thisway the electronic timing action may be prematurely terminated and hencethe unlocking of the shutter drive by an operation to be effected by thephotographer at the end of an exposure is canceled.

Preferably the switch is located in the path of the camera cocking leverand is adapted to be actuated directly thereby. In one form of theinvention the switch has a displaceable contact spring supported againstthe cocking lever and following the operating movement of this lever,the spring cooperating with a further fixed contact spring.

An embodiment of the invention is illustrated in the accompanyingdrawings and is described in detail below. In the drawings:

FIG. 1 shows a shutter with an electronic timing device in the cockedposition; the switch short circuiting the photoelectric resistor isopened by the camera cocking lever located in the normal position;

FIG. 2 is a view of part of the shutter shown in FIG. 1, the bladedriving mechanism of which is blocked in the open position of theblades;

FIG. 3 shows the shutter part of FIG. 2 with the blade driving mechanismin a movement phase during the closing process; and

FIG. 4 is a fragmentary section on the line IV-IV of FIG. 2.

In a housing 1 of a photographic shutter a base plate 2 with a tubularsocket 2a is arranged, to mount the shutter-driving device. The latterconsists of a driving disc 5 mounted on a cocking shaft 4, a drivingspring 6 acting thereon and a driving member or pawl 7 connected to thedriving disc, the free end of paw], which is provided with a lug 8a,cooperating with an actuating part 8 of the blades 9 formed as a ring sothat the action of the driving ring always occurs from a normal positionin a clockwise direction of the blade ring, the blades executing areciprocating movement. A two-armed stop lever 10 is used to lock thedriving disc 5 in the cocked position as shown in FIG. 1. a furthertwo-armed release lever 11 indicated in this view engaging with onelever arm thereof. This lever 11 is actuated by means of a camerarelease member 12 shown only in part in FIG. 1, via further intermediatemembers which are shown by a chain-dotted line.

To retain the blades 9 in the open position for the duration of theexposure time determined by an electronic timing device described below,the blade ring 8 has a further lug 8b passing through a slot, (notshown) in the base plate 2, in front of which, as shown in FIGS. 2 to 4,a spring-loaded stop catch 14 assumes a position with its lug 14a in theopen position of the blades 9. This catch mounted on a spigot 15,carries a pin 14b, and is urged by a spring 16 into the stop position.To disengage the catch 14 from the stop position at the end of thetiming procedure an armature lever 18 mounted on a pin 17 is provided,on which there is a lifting arm 18a cooperating with the pin 14b of thecatch. On the free end of the lever 18 there is an armature 20 actedupon by an electromagnet 21 connected in the circuit of the electronictiming device. The armature lever 18 during the cocking procedure ispressed against the electromagnet 21. For this purpose there is a lever24 mounted on a pin 23 which, when the driving disc 5 is transferredinto the cocking position, is rotated in a clockwise direction by meansof a pin 5a of this disc and by means of a pin 24a causes the armaturelever to abut with its free end against the electromagnet 21, againstthe action of a return spring 25.

In the embodiment of an electronic shutter shown in the drawings, thedriving disc 5 is moved into the cocking position in known manner bymeans of a camera cocking lever 27 arranged on the camera, which leveralso acts on a film transfer device. The engagement between cockinglever 27 and the cocking shaft 4 carrying the driving disc 5 isindicated in the drawing merely by the chain-dotted line 28. A spring 29retains the cocking lever 27 in abutment against a fixed pin 30 whichdetermines the normal position of this lever.

The above-mentioned electronic timing device is a known transistorizedrelaxation circuit and therefore is not shown in further detail. Thiscircuit includes an electronic switch 32, which cooperates with a RCcircuit including a photoelectric resistor R and capacitor C whichdetermines the duration of the exposure time; the circuit energizes theelectromagnet 21. A contact switch S which is closed when the releaselever 12 is actuated serves to connect the electronic time controlcircuit to a battery B. A further contact switch S formed as achangeover switch is provided to short circuit the capacitor C in thecontact position (FIG. 1) corresponding to the closed position of theshutter. The beginning of the opening movement of the blade ring 8 movesthis switch to initiate the charging of the capacitor and establishes aparallel connection to the switch 8,. To actuate the changeover switch Sa pin is provided on the blade ring 8, which pin, in the normal positionof the blade ring, retains the changeover switch in the contact positionshown. When the blade ring 8 commences to move, the contact blade of thechangeover switch 8, follows pin 8c and changes over into the othercontact position, not shown.

As already indicated, the stop lever 14 is moved out of its stopposition at the end of the timing procedure by the armature lever 18.When taking a photograph with a relatively long exposure time, thephotographer may attempt to recock the shutter although the action ofthe electronic timing device-has not yet been completed. This isprevented by the pawl 14 which is still in the stop position, becauseduring a cocking movement from the open position shown in FIG. 2 thedriving disc 5 tries to drive the blade ring 8 in an anticlockwisedirection. This rotary movement of the blade ring 8 is prevented by thepawl 14 which is still located in the stop position, so that if force isexerted the mechanism could be damaged or broken. To prevent damage tothe mechanical gear train, the aforesaid shutter arrangement has anadditional operating device provided which during a premature cockingprocedure overrides and terminates the exposure timing and hence cancelsthe blocking of the shutter drive. This device consists of a furtherswitch S in the circuit of the electronic timing device, by means ofwhich when the camera is cocked, a short circuit is produced across thephotoelectric resistor R. To actuate thisswitch S the camera cockinglever 27 is used, the pin 27a of which cooperates with a contact spring33 of the switch, which consists of this spring and a further contactspring 34. The arrangement is such that in the normal position of thecamera cocking lever the contact spring 33, as shown in FIG. 1, issupported against the pin 27a, causing the switch S to open. When thecocking lever 27 of the camera is moved in the direction indicated bythe arrow, the contact spring 33, following the pin 27a, abuts againstthe contact spring 34 thus short circuiting the photoelectric resistorR.

When taking a photograph the switch S is open and there fore does notaffect the electronic timing device. When the release 12 is depressed,switch S is closed, and the driving disc simultaneously released byrotation of the stop lever in a clockwise direction. The disc 5 nowmoves under the influence of the spring 6, the blade ring 8 being driveninto the open position as shown in FIG. 2, in which the pawl 14 with itslug 14a assumes a position in front of the lug 8b of the blade ring, sothat the driving mechanism is blocked. Closure of the switch S causesthe electromagnet 21 and the electronic timing device to be connected tothe battery B. The electromagnet 21 retains the armature lever 18 in theposition shown in FIG. 1 after the driving disc 5 has started. Theswitch S in the first phase of movement of the blade ring 8 changes overinto its other contact position, causing the capacitor C to be chargedand hence the timing in the electronic control circuit to begin. Thetime taken to charge the capacitor C to the operating value of theelectronic switch 32 is dependent upon the resistance value of thephotoelectric resistor R, which itself is dependent upon the ambientlight. When finally the capacitor C has reached this operating value,then the electronic switch 32 reverses and the magnetic field of theelectromagnet 21 collapses. The return spring now swings the armaturelever 18 in a clockwise direction, causing the lifting arm 18a to movethe pawl 14 out of the stop position, so as to allow the shutter toclose again (FIG. 3). If subsequently the shutter is again cocked bymovement of the camera cocking lever 27 in the direction of the arrow,then the switch s closcs briefly but this does not affect the electronictiming device, since the timing procedure has ended.

Should it occur that the photographer attempts to recock the shutterbefore the exposure, based on prevailing low light conditions, has notended, as a consequence of which the blade ring 8 is still blocked, thenthe action of the electronic timing device is prematurely terminated.This is effected by closing the switch S with the first movement strokeof the camera cocking lever 27 and applying a short circuit to thephotoelectric resistor R, which immediately alters the state of chargeof the capacitor C. Consequently the electronic timing device operatesimmediately, which in turn results in the cancellation of the blockingof the shutter drive and initiates a closing movement of the shutterblade system.

Iclaim:

1. A photographic shutter including a driving member which when movedfrom a normal position opens and then closes the shutter by means of areciprocating actuating member, an electronic timing device controllingan armature lever biased by a return spring with the aid of aphotoelectric resistor in dependence upon the ambient light, saidarmature lever cooperating with a pawl blocking the actuating member inthe open position of the blades for the duration of the timing, whereina switch connected in the circuit of the electronic timing device closesa contact when the cocking mechanism of the camera is actuated, saidcontact short circuiting the photoelectric resistor.

2. A photographic shutter according to claim 1, wherein the switch islocated in the path of the cocking lever of the camera and is actuateddirectlK thereby.

3. A photographic s utter according to claim 2, wherein the switch has adisplaceable contact spring supported against the cocking lever andfollowing the movement of this lever, which spring cooperates with afurther fixed contact spring.

1. A photographic shutter including a driving member which when movedfrom a normal position opens and then closes the shutter by means of areciprocating actuating member, an electronic timing device controllingan armature lever biased by a return spring with the aid of aphotoelectric resistor in dependence upon the ambient light, saidarmature lever cooperating with a pawl blocking the actuating member inthe open position of the blades for the duration of the timing, whereina switch connected in the circuit of the electronic timing device closesa contact when the cocking mechanism of the camera is actuated, saidcontact short circuiting the photoelectric resistor.
 2. A photographicshutter according to claim 1, wherein the switch is located in the pathof the cocking lever of the camera and is actuated directly thereby. 3.A photographic shutter according to claim 2, wherein the switch has adisplaceable contact spring supported against the cocking lever andfollowing the movement of this lever, which spring cooperates with afurther fixed contact spring.